Semiconductor memory device and method for manufacturing same

ABSTRACT

According to one embodiment, the array chip includes a three-dimensionally disposed plurality of memory cells and a memory-side interconnection layer connected to the memory cells. The circuit chip includes a substrate, a control circuit provided on the substrate, and a circuit-side interconnection layer provided on the control circuit and connected to the control circuit. The circuit chip is stuck to the array chip with the circuit-side interconnection layer facing to the memory-side interconnection layer. The bonding metal is provided between the memory-side interconnection layer and the circuit-side interconnection layer. The bonding metal is bonded to the memory-side interconnection layer and the circuit-side interconnection layer.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of and claims the benefit of priorityunder 35 U.S.C. §120 from U.S. Ser. No. 14/806,034 filed Jul. 22, 2015,and claims the benefit of priority under 35 U.S.C. §119 from JapanesePatent Application No. 2014-186684 filed Sep. 12, 2014; the entirecontents of each of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a semiconductor memorydevice and a method for manufacturing a semiconductor memory device.

BACKGROUND

A memory device having a three-dimensional structure has been proposed.In the memory device, a memory hole is formed in a stacked bodyincluding a plurality of electrode layers stacked via insulating layers.The electrode layers function as control gates in memory cells. Asilicon body functioning as a channel is provided on the sidewall of thememory hole via a charge storage film.

In order to reduce a space factor of a control circuit of athree-dimensional memory array in a chip, there has also been proposed atechnique for providing the control circuit right under the array. Forexample, a configuration is proposed in which bit lines are connected totransistors formed on a substrate, via contact plugs formed at an arrayend portion and a bit line extension layer provided on the lower side ofa memory array.

Therefore, a fine interconnection layer equivalent to the bit lines isalso necessary under the array. A region around the array is necessaryin order to form a deep contact. Further, there is a concern about aproblem in that, for example, the bit lines are substantially long, abit line capacity increase, and operation speed is affected.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view of a semiconductor memory device ofan embodiment;

FIG. 2 is a schematic plan view showing an example of a layout of abonding metal of the semiconductor memory device of the embodiment;

FIG. 3 is a schematic perspective view of a memory cell array of theembodiment;

FIG. 4 is a schematic sectional view of a memory string of theembodiment;

FIG. 5 is a schematic sectional view of a memory cell of the embodiment;

FIG. 6 and FIG. 7 are schematic sectional views showing a method formanufacturing the semiconductor memory device of the embodiment;

FIG. 8 is a schematic sectional view of the semiconductor memory deviceof the embodiment;

FIG. 9 is a schematic sectional view of the semiconductor memory deviceof the embodiment; and

FIG. 10 is a schematic perspective view of a memory cell array of theembodiment.

DETAILED DESCRIPTION

According to one embodiment, a semiconductor memory device includes anarray chip, a circuit chip, a bonding metal, a pad, and an externalconnection electrode. The array chip includes a three-dimensionallydisposed plurality of memory cells and a memory-side interconnectionlayer connected to the memory cells. The array chip does not include asubstrate. The circuit chip includes a substrate, a control circuitprovided on the substrate, and a circuit-side interconnection layerprovided on the control circuit and connected to the control circuit.The circuit chip is stuck to the array chip with the circuit-sideinterconnection layer facing to the memory-side interconnection layer.The bonding metal is provided between the memory-side interconnectionlayer and the circuit-side interconnection layer. The bonding metal isbonded to the memory-side interconnection layer and the circuit-sideinterconnection layer. The pad is provided in the array chip. Theexternal connection electrode reaches the pad from a surface side of thearray chip.

Embodiments are described below with reference to the drawings. Notethat, in the figures, the same components are denoted by the samereference numerals and signs.

FIG. 1 is a schematic sectional view of a semiconductor memory device ofan embodiment.

The semiconductor memory device of the embodiment has a structure inwhich an array chip 100 including a three-dimensionally disposedplurality of memory cells and a circuit chip 200 including a controlcircuit that controls writing, erasing, and readout of data for a memorycell are stuck together.

As described below, after an array wafer and a circuit wafer are stucktogether wafer-to-wafer, a wafer bonded body is diced and singulatedinto chips.

First, the array chip 100 is described. The array chip 100 includes amemory cell array 1 of a three-dimensional structure.

FIG. 3 is a schematic perspective view of the memory cell array 1. Notethat, in FIG. 3, to clearly show the figure, an interlayer insulatinglayer, an insulating separation film, and the like are not shown.

In FIG. 3, two directions that are orthogonal to each other arerepresented as an X-direction and a Y-direction. A direction that isorthogonal to the X-direction and the Y-direction (an XY plane) and inwhich a plurality of layers of electrode layers WL are stacked isrepresented as Z-direction (a stacking direction).

The memory cell array 1 includes a plurality of memory strings MS. FIG.4 is a schematic sectional view of the memory string MS. FIG. 4 shows across section parallel to a YZ plane in FIG. 3.

The memory cell array 1 includes a stacked body including a plurality ofelectrode layers WL and a plurality of insulating layers 40. Theelectrode layers WL and the insulating layers 40 are alternatelystacked. The stacked body is provided on a back gate BG functioning as alower gate layer. Note that the number of layers of the electrode layersWL shown in the figure is an example. The number of layers of theelectrode layers WL may be any number.

As shown in FIG. 6 referred to below, the back gate BG is provided on afirst substrate 10 via insulating films 48 and 45. After an array waferW1 and a circuit wafer W2 are stuck together, the first substrate isremoved.

The back gate BG and the electrode layers WL are layers containingsilicon as a main component. Further, the back gate BG and the electrodelayers WL contain, for example, boron as impurities for impartingconductivity to a silicon layer. The electrode layers WL may containmetal silicide. Alternatively, the electrode layers WL are metal layers.

The insulating layers 40 mainly contain, for example, silicon oxide. Forexample, the insulating film 48 is a silicon oxide film and theinsulating film 45 is a silicon nitride film.

One memory string MS is formed in a U shape including a pair of acolumnar sections CL extending in the Z-direction and a connectingsection JP that couples respective lower ends of the pair of columnarsections CL. The columnar sections CL are formed in, for example, acolumnar or elliptical columnar shape, pierce through the stacked body,and reach the back gate BG.

A drain-side select gate SGD is provided at an upper end portion of oneof the pair of columnar sections CL in the U-shaped memory string MS. Asource-side select gate SGS is provided at the other upper end portion.The drain-side select gate SGD and the source-side select gate SGS areprovided on the electrode layer WL of the top layer via an interlayerinsulating layer 43.

The drain-side select gate SGD and the source-side select gate SGS arelayers containing silicon as a main component. Further, the drain-sideselect gate SGD and the source-side select gate SGS contain, forexample, boron as impurities for imparting conductivity to a siliconlayer.

The drain-side select gate SGD and the source-side select gate SGSfunctioning as an upper select gate and the back gate BG functioning asa lower select gate are thicker than one layer of the electrode layerWL.

The drain-side select gate SGD and the source-side select gate SGS areseparated in the Y-direction by an insulating separation film 47. Astacked body under the drain-side select gate SGD and a stacked bodyunder the source-side select gate SGS are separated in the Y-directionby an insulating separation film 46. That is, a stacked body between thepair of columnar sections CL of the memory string MS is separated in theY-direction by the insulating separation films 46 and 47.

On the source-side select gate SGS, a source line (e.g., a metal film)SL is provided via an insulating layer 44. A plurality of bit lines(e.g., metal films) BL shown in FIG. 1 are provided on the drain-sideselect gate SGD and the source line SL via the insulating layer 44. Thebit lines BL extend in the Y-direction.

FIG. 5 is an enlarged schematic sectional view of a part of the columnarsection CL.

The columnar section CL is formed in a U-shaped memory hole formed inthe stacked body including the plurality of layers of the electrodelayers WL, the plurality of layers of the insulating layers 40, and theback gate BG. In the memory hole, a channel body 20 functioning as asemiconductor body is provided. The channel body 20 is, for example, asilicon film. The impurity concentration of the channel body 20 is lowerthan the impurity concentration of the electrode layers WL.

A memory film 30 is provided between the inner wall of the memory holeand the channel body 20. The memory film 30 includes a block insulatingfilm 35, a charge storage film 32, and a tunnel insulating film 31.

The block insulating film 35, the charge storage film 32, and the tunnelinsulating film 31 are provided in order from the electrode layers WLside between the electrode layers WL and the channel body 20.

The channel body 20 is provided in a cylindrical shape extending in thestacking direction of the stacked body. The memory film 30 is providedin a cylindrical shape to surround the outer circumferential surface ofthe channel body 20 while extending in the stacking direction of thestacked body. The electrode layers WL surround the channel body 20 viathe memory film 30. A core insulating film 50 is provided on the innerside of the channel body 20. The core insulating film 50 is, forexample, a silicon oxide film.

The block insulating film 35 is in contact with the electrode layers WL.The tunnel insulating film 31 is in contact with the channel body 20.The charge storage film 32 is provided between the block insulating film35 and the tunnel insulating film 31.

The channel body 20 functions as a channel in memory cells MC. Theelectrode layers WL function as control gates of the memory cells. Thecharge storage film 32 functions as a data memory layer that accumulatescharges injected from the channel body 20. That is, the memory cells MChaving a structure in which the control gates surround the channel areformed in crossing portions of the channel body 20 and the electrodelayers WL.

The semiconductor memory device of the embodiment is a nonvolatilesemiconductor memory device that can electrically freely perform erasingand writing of data and can retain stored content even if a power supplyis turned off.

The memory cell MC is, for example, a memory cell of a charge trap type.The charge storage film 32 includes a large number of trap sites thattrap charges. The charge storage film 32 is, for example, a siliconnitride film.

The tunnel insulating film 31 functions as a potential barrier whencharges are injected into the charge storage film 32 from the channelbody 20 or when charges stored in the charge storage film 32 diffuse tothe channel body 20. The tunnel insulating film 31 is, for example, asilicon oxide film.

Alternatively, as the tunnel insulating film, a stacked film (an ONOfilm) having a structure in which a silicon nitride film is sandwichedby a pair of silicon oxide films may be used. When the ONO film is usedas the tunnel insulating film, compared with a single layer of a siliconoxide film, an erasing operation can be performed in a low electricfield.

The block insulating film 35 prevents the charges stored in the chargestorage film 32 from diffusing to the electrode layers WL. The blockinsulating film 35 includes a cap film 34 provided in contact with theelectrode layers WL and a block film 33 provided between the cap film 34and the charge storage film 32.

The block film 33 is, for example, a silicon oxide film. The cap film 34is a film having a dielectric constant higher than the dielectricconstant of silicon oxide and is, for example, a silicon nitride film.By providing such a cap film 34 in contact with the electrode layers WL,it is possible to suppress back tunnel electrons injected from theelectrode layers WL during erasing. That is, by using a stacked film ofthe silicon oxide film and the silicon nitride film as the blockinsulating film 35, it is possible to improve a charge blockingproperty.

As shown in FIGS. 3 and 4, a drain-side select transistor STD isprovided at the upper end portion of one of the pair of columnarsections CL in the U-shaped memory string MS. A source-side selecttransistor STS is provided at the other upper end portion.

The memory cell MC, the drain-side select transistor STD, and thesource-side select transistor STS are vertical transistors in which anelectric current flows in the stacking direction of the stacked body(the Z-direction).

The drain-side select gate SGD functions as a gate electrode (a controlgate) of the drain-side select transistor STD. An insulating film 51(FIG. 4) functioning as a gate insulating film of the drain-side selecttransistor STD is provided between the drain-side select gate SGD andthe channel body 20. The channel body 20 of the drain-side selecttransistor STD is connected to the bit line BL above the drain-sideselect gate SGD.

The source-side select gate SGS functions as a gate electrode (a controlgate) of the source-side select transistor STS. An insulating film 52(FIG. 4) functioning as a gate insulating film of the source-side selecttransistor STS is provided between the source-side select gate SGS andthe channel body 20. The channel body 20 of the source-side selecttransistor STS is connected to the source line SL above the source-sideselect gate SGS.

A back gate transistor BGT is provided in the connecting section JP ofthe memory string MS. The back gate BG functions as a gate electrode (acontrol gate) of the back gate transistor BGT. The memory film 30provided in the back gate BG functions as a gate insulating film of theback gate transistor BGT.

A plurality of memory cells MC including the electrode layers WL of therespective layers as control gates are provided between the drain-sideselect transistor STD and the back gate transistor BGT. Similarly, aplurality of memory cells MC including the electrode layers WL of therespective layers as control gates are also provided between the backgate transistor BGT and the source-side select transistor STS.

The plurality of memory cells MC, the drain-side select transistor STD,the back gate transistor BGT, and the source-side select transistor STSare connected in series through the channel body 20 and configuresU-shaped one memory string MS. The plurality of the memory strings MSare arrayed in the X-direction and the Y-direction, whereby theplurality of memory cells MC are three-dimensionally provided in theX-direction, the Y-direction, and the Z-direction.

The electrode layers WL are separated into a plurality of blocks in theY-direction and extend in the X-direction.

In FIG. 1, a region at the end in the X-direction in the memory cellarray 1 is shown. A step structure section 96 of the electrode layers WLis formed at an end of a memory cell array region 81 where the pluralityof memory cells MC are disposed.

In the step structure section 96, the end portions in the X-direction ofthe electrode layers WL of the respective layers are formed in a stepshape. In the step structure section 96, a plurality of contact plugs 61connected to the electrode layers WL of the respective layers formed inthe step shape are provided. The contact plugs 61 are connected to theelectrode layers WL of the respective layers in the step shape piercingthrough an interlayer insulating layer 69.

In the step structure section 96, the back gate BG is connected to acontact plug 63. A select gate SG (the drain-side select gate SGD andthe source-side select gate SGS) is connected to a contact plug 65.

The contact plugs 61 connected to the electrode layers WL are connectedto word interconnection layers 62. The contact plug 63 connected to theback gate BG is connected to a back gate interconnection layer 64. Thecontact plug 65 connected to the select gate SG is connected to a selectgate interconnection layer 66.

The word interconnection layers 62, the back gate interconnection layer64, and the select gate interconnection layer 66 are provided in thesame layer. The source line SL shown in FIG. 3 is also provided in thesame layer as the word interconnection layers 62, the back gateinterconnection layer 64, and the select gate interconnection layer 66.

The word interconnection layers 62, the back gate interconnection layer64, the select gate interconnection layer 66, and the source line SL areformed by patterning of the same material layer (e.g., metal layer).Therefore, the word interconnection layers 62, the back gateinterconnection layer 64, the select gate interconnection layer 66, andthe source line SL are simultaneously formed in the same layer formed ofthe same material and at the same thickness.

The word interconnection layers 62 are further connected to surfacelayer interconnection layers 73, which are formed on the side of abonding surface to the circuit chip 200 of the array chip 100, via otherplugs and interconnection layers.

The back gate interconnection layer 64, the select gate interconnectionlayer 66, and the source line SL are also connected to the surface layerinterconnection layers 73 via other plugs and interconnection layers.

The channel bodies 20 of the columnar sections CL and the bit lines BLare connected via plugs 67. Further, the bit lines BL are connected tothe surface layer interconnection layers 73 via other plugs andinterconnection layers.

The array chip 100 includes a memory-side interconnection layer forelectrically connecting the memory cell array 1 to the circuit chip 200.The memory-side interconnection layer is formed as a multilayerinterconnect including the word interconnection layers 62, the back gateinterconnection layer 64, the select gate interconnection layer 66, andthe surface layer interconnection layers 73.

The surface layer interconnection layers 73 are connected tocircuit-side interconnection layers 76 of the circuit chip 200 viabonding metals 74 a and 74 b. The circuit chip 200 includes a substrate5. The substrate 5 is, for example, a silicon substrate.

A control circuit is formed on a circuit formation surface (a surfacefacing the array chip 100 side) of the substrate 5. The control circuitis formed as a semiconductor integrated circuit including a transistor77. The transistor 77 has a Metal-Oxide-Semiconductor Field EffectTransistor (MOSFET) structure including, for example, a gate electrode78 and source/drain regions. The source/drain regions of the MOSFET areconnected to the circuit-side interconnection layers 76 via plugs 79.

The circuit-side interconnection layers 76 are formed on the circuitformation surface as a multilayer interconnect via an interlayerinsulating film 80.

The bonding metals 74 a and 74 b are provided between the surface layerinterconnection layers 73 of the array chip 100 and interconnectionlayers of uppermost layers (interconnection layers of top layers viewedfrom the substrate 5) of the circuit-side interconnection layers 76 ofthe circuit chip 200. The bonding metals 74 a and 74 b are, for example,copper or a copper alloy containing copper as a main component.

The surface layer interconnection layers 73 of the array chip 100 andthe circuit-side interconnection layers 76 of the top layer of thecircuit chip 200 are bonded to the bonding metals 74 a and 74 b. Aninsulating film 75 is provided around the bonding metals 74 a and 74 bbetween the array chip 100 and the circuit chip 200. The insulating film75 is a resin film or an inorganic film.

The array chip 100 and the circuit chip 200 are stuck together via thebonding metals 74 a and 74 b and the insulating film 75. The memory-sideinterconnection layer of the array chip 100 and the circuit-sideinterconnection layers 76 of the circuit chip 200 are electricallyconnected via the bonding metals 74 a and 74 b.

Therefore, the memory cell array 1 is connected to the control circuitof the circuit chip 200 via the memory-side interconnection layer, thebonding metals 74 a and 74 b, and the circuit-side interconnectionlayers 76.

According to the embodiment, an external connection electrode 71 isformed on the array chip 100 side. A pad 70 is provided in a regioncloser to an end than the step structure section 96 in the array chip100.

For example, the pad 70 is formed by patterning of a metal layer (e.g.,a tungsten layer) in forming the word interconnection layers 62, theback gate interconnection layer 64, the select gate interconnectionlayer 66, and the source line SL. Therefore, the pad 70 is formed in thesame layer and formed of the same material and at the same thickness asthe word interconnection layers 62, the back gate interconnection layer64, the select gate interconnection layer 66, and the source line SL.

An external connection pad 72 is provided on the surface (the surface onthe opposite side of the bonding surface to the circuit chip 200) of thearray chip 100. The external connection electrode 71 is provided betweenthe external connection pad 72 and the pad 70.

The pad 70 is electrically connected to the circuit-side interconnectionlayers 76 via the memory-side interconnection layer orseparately-provided vias. Therefore, the control circuit formed in thecircuit chip 200 is electrically connected to the external connectionpad 72 via the pad 70 and the external connection electrode 71. Theexternal connection pad 72 is connectable to a mounting substrate orother chips via, for example, a solder ball, a metal bump, or a bondingwire.

A plurality of the bonding metals 74 a and 74 b are disposed in abonding section of the array chip 100 and the circuit chip 200. Theplurality of bonding metals 74 a and 74 b mainly include a plurality ofbit-line lead-out sections 74 a electrically connected to the bit linesBL and a plurality of word-line lead-out sections 74 b electricallyconnected to the electrode layers WL.

FIG. 2 is a schematic plan view showing a disposition relation of thebit-line lead-out sections 74 a and the word-line lead-out sections 74b.

The bit-line lead-out sections 74 a are disposed in a regionoverlapping, in the stacking direction, a memory cell array region 81where the plurality of memory strings MS are disposed (a region belowthe memory cell array region 81 in FIG. 1).

The word-line lead-out sections 74 b are disposed in a regionoverlapping, in the stacking direction, a region where the stepstructure section 96, the external connection electrode 71, and the likeare formed further on the outer side than the memory cell array region81. In FIG. 1, the plurality of word-line lead-out sections 74 b aredisposed in a region below the step structure section 96 and a regionbelow the external connection electrode 71 (the pad 70).

A method for manufacturing the semiconductor memory device of theembodiment is described with reference to FIGS. 6 and 7.

Components of the array chip 100 and components of the circuit chip 200are respectively formed in wafer states.

In FIG. 6, the array wafer W1 and the circuit wafer W2 before beingstuck together are shown.

The substrate 10 still remains on the array wafer W1 before being stuck.The back gate BG is formed on the substrate (e.g., a silicon substrate)10 via the silicon oxide film 48 and the silicon nitride film 45.Further, the stacked body including the plurality of layers of theelectrode layers WL and the select gate SG are stacked on the back gateBG.

After the stacked body is formed, the memory strings MS, the stepstructure section 96, and the like are formed. Further, the memory-sideinterconnection layer is formed. The pad 70 is also formed during theformation of the memory-side interconnection layer.

After the surface layer interconnection layers 73 of the memory-sideinterconnection layer is formed, first bonding metals 91 and a firstinsulating film 92 are formed on a bonding surface (the surface on theopposite side of the substrate 10) of the array wafer W1. The firstbonding metals 91 are bonded to the surface layer interconnection layers73. The first insulating film 92 is formed between the first bondingmetal 91 and the first bonding metal 91 (around the first bonding metals91). The surfaces (bonding surfaces) of the first bonding metals 91 areexposed from the first insulating film 92.

Components of the circuit wafer W2 are formed on the substrate (e.g., asilicon substrate) 5 different from the substrate 10 of the array waferW1.

After the control circuit (the semiconductor integrated circuit)including the transistor 77 is formed on the surface of the substrate 5,the circuit-side interconnection layers 76 are formed via the interlayerinsulating layer 80.

Second bonding metals 93 and a second insulating film 94 are formed on abonding surface (the surface on the opposite side of the substrate 5) ofthe circuit wafer W2. The second bonding metals 93 are bonded to thecircuit interconnection layers 76 of the top layers. The secondinsulating film 94 is formed between the second bonding metal 93 and thesecond bonding metal 93 (around the second bonding metals 93). Thesurfaces (bonding surfaces) of the second bonding metals 93 are exposedfrom the second insulating film 94.

The array wafer W1 and the circuit wafer W2 are bonded wafer-to-wafer byapplying mechanical pressure with the surfaces on the opposite sides ofthe substrates 10 and 5 facing to each other.

The first bonding metals 91 and the second bonding metals 93 are, forexample, copper or a copper alloy. The first bonding metals 91 and thesecond bonding metals 93 are bonded to each other to be integral bondedmetals 74 as shown in FIG. 7. The first insulating film 92 and thesecond insulating film 94 are bonded to be an integral insulating film75.

After the array wafer W1 and the circuit wafer W2 are stuck together,the substrate 10 of the array wafer W1 is removed. For example, theentire substrate 10 is removed by wet etching using nitrohydrofluoricacid.

On a surface from which the substrate 10 is removed, the insulatingfilms (the silicon oxide film 48 and the silicon nitride film 45) formedon the substrate 10 remain as a passivation film that protects thesurface of the array wafer W1 (the array chip 100).

After the substrate 10 is removed, a via 95 reaching the pad 70 isformed from the side of the surface from which the substrate 10 isremoved (the surface of the silicon oxide film 48). In the via 95, asshown in FIG. 1, the external connection electrode 71 is embedded.

Alternatively, the external connection electrode 71 may be formed on thebottom section of the via 95 (the upper surface of the pad 70) and thesidewall of the via 95 while leaving a space in the via 95.

For driving of the memory cell array 1, a high voltage of, for example,approximately 20 V is sometimes required. In order to maintain abreakdown voltage of the transistor 77 of the control circuit (a CMOScircuit) (in order to extend a depletion layer), it is desired to leave,on the circuit chip 200 side, the substrate (the silicon substrate) 5having thickness of approximately 10 to 20 μm. The thick substrate 5functions as a support body for the semiconductor memory device.

In connecting the control circuit to an external circuit, it isconceivable to form Through Silicon Vias (TSVs), which pierce throughthe substrate 5, from the rear surface side of the substrate 5 andconnect the TSVs to the circuit-side interconnection layers 76. However,costs and a treatment time for etching of the thick substrate 5 arelarge. Further, in order to prevent a short circuit of the siliconsubstrate 5 and intra-via electrodes, a process for forming insulatingfilms on via sidewalls is also necessary.

On the other hand, according to the embodiment, the via 95 (FIG. 7) isformed on the side of the array chip 100 from which the substrate 10 isremoved. Since the thickness of the array chip 100 is approximatelyseveral micrometers, a deep etching process for piercing through a thicksubstrate of several tens micrometers is unnecessary. It is possible toattain a reduction in costs.

By removing the substrate 10 of the array wafer W1 with wet etching,stress applied to the memory cell array 1 is not generated unlikesubstrate removal by grinding. Therefore, yield and reliability areimproved.

A method for forming a control circuit on a substrate and forming amemory cell array on the control circuit is also conceivable. However,in some case, a heat process of 900° C. or higher is necessary for theformation of the three-dimensional memory cell array 1. If the controlcircuit is formed under the cell array in advance, there is a concernabout problems such as diffusion of impurities of a transistor and heatresistance of a metal contact.

Further, according to an increase in speed of an interface in future,improvement of the performance of the transistor is desired. It is alsolikely that it is necessary to form the control circuit using a processwith low heat resistance in which salicide or the like is used.

On the other hand, according to the embodiment, since the array chip 100including the memory cell array 1 and the circuit chip 200 including thecontrol circuit are formed by separate wafer processes, high heattreatment for the memory cell array 1 does not act on the controlcircuit. Therefore, it is possible to form both of the memory cell array1 and the control circuit in structures with high reliability.

In a structure in which a control circuit and a memory cell array aresequentially formed on a substrate, bit lines are formed further on theupper side than a stacked body when viewed from the substrate.Therefore, in connecting the bit lines to the control circuit, after thebit lines are led out to an outer side region of a memory cell arrayregion via an interconnection layer formed on the bit lines, deepcontact plugs are connected to the control circuit on the substratesurface from the lead-out interconnection layer. This could be a causeof an increase in a chip area because of a region for routing ofinterconnects. There is also a concern that the bit lines aresubstantially long, a bit line capacity increases, and operation speedis affected. There is the same concern about routing of electrode layers(word lines).

On the other hand, according to the embodiment, the side where the bitlines BL, the source line SL, the word interconnection layers 62, andthe like are formed is bonded to the circuit chip 200 via the bondingmetals 74 a and 74 b. Therefore, interconnects only have to be directlyled out downward (toward the bonding surface side).

For example, as described with reference to FIG. 2, the bit-linelead-out sections 74 a are not led out to (not disposed on) the outerside of the memory cell array region 81 and are disposed in theoverlapping region below the memory cell array region 81.

Therefore, it is possible to suppress an increase in a interconnectionlength and an interconnect formation region for connecting the bit linesBL, the source line SL, the word interconnection layers 62, and the liketo the control circuit and suppress an operation delay and an increasein a chip area.

As described above, according to the embodiment, it is possible toattain an increase in the capacity of the memory cells and improvementof reliability with an inexpensive process. Further, it is possible torealize refining and an increase in speed of the control circuit.

The pad connected to the external connection electrode may be formed inthe same layer as the back gate BG as shown in FIG. 8.

Polycrystalline silicon is often used in the back gate BG. Therefore, inorder to reduce the resistance of the pad, it is desired to stack alayer 110 containing metal such as a metal silicide layer or a metallayer on the back gate BG.

The layer 110 containing the metal is formed on the substrate 10 via theinsulating films 48 and 45 in a wafer stage. The back gate BG is formedon the layer 110. The layer 110 containing the metal and the back gateBG are left as pads 110 and 111 in a region further on the outer sidethan the step structure section 96 by patterning.

After the substrate 10 is removed, a via reaching the pad 110 is formedfrom the surface side of the array wafer W1. An external connectionelectrode 112 is formed in the via.

Compared with the structure shown in FIG. 1 in which the pad is formedin the same layer as the word interconnection layer 62 and the like, thevia may be shallow. It is possible to realize a further reduction incosts and further improvement of yield.

The pad is not limited to be formed in the array chip 100. As shown inFIG. 9, a part of the circuit-side interconnection layer 76 of thecircuit chip 200 may be used as a pad 122. For example, ainterconnection layer of a top layer of the circuit-side interconnectionlayer 76 viewed from the substrate 5 is formed as the pad 122.

After the substrate 10 of the array wafer W1 is removed, a via reachingthe pad 122 is formed from the surface side of the array wafer W1 in aregion further on the outer side than the step structure section 96. Anexternal connection electrode 121 is formed in the via. The externalconnection electrode 121 is connected to the circuit-sideinterconnection layer 76 not via the memory-side interconnection layer.

FIG. 10 is a schematic perspective view of a memory cell array 2 ofanother example of the semiconductor memory device of the embodiment.Note that, in FIG. 10, as in FIG. 3, to clearly show the figure,insulating layers and the like are not shown.

The source layer SL is provided on the opposite side of the bondingsurface to the circuit chip 200. The source-side select gate (the lowerselect gate layer) SGS is provided on the source layer SL via aninsulating layer.

An insulating layer is provided on the source-side select gate SGS. Astacked body obtained by alternately stacking the plurality of electrodelayers WL and a plurality of insulating layers is provided on theinsulating layer.

An insulating layer is provided on the electrode layer WL of a mostdistant layer when viewed from the source layer SL. The drain-sideselect gate (the upper select gate layer) SGD is provided on theinsulating layer.

The columnar sections CL extending in the Z-direction are provided inthe stacked body. That is, the columnar sections CL pierce through thedrain-side select gate SGD, the plurality of layers of the electrodelayers WL, and the source-side select gate SGS. One end of the channelbody 20 in the columnar section CL is connected to the bit line BL. Theother end of the channel body 20 is connected to the source line SL.

The source line SL is formed on the substrate. The source-side selectgate SGS, the stacked body including the plurality of layers of theelectrode layers WL, the drain-side select gate SGD, and the bit linesBL are formed in order on the source line SL. An array wafer in whichthe source line SL, the source-side select gate SGS, the stacked bodyincluding the plurality of layers of the electrode layers WL, thedrain-side select gate SGD, and the bit lines BL is stuck to the circuitwafer W2 with the bit lines BL side opposed to the circuit wafer W2.

After the sticking, the substrate is removed. A via is formed from asurface side from which the substrate is removed. An external connectionelectrode is formed in the via.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modification as would fall within the scope andspirit of the inventions.

What is claimed is:
 1. A semiconductor memory device comprising: a firststructure including a substrate, a control circuit disposed on thesubstrate, and a first interconnection disposed on the control circuit;and a second structure disposed on the first structure, the secondstructure including a second interconnection, a bit line, asemiconductor body, a plurality of conductive layers, and a chargestorage portion, the second interconnection electrically connected tothe first interconnection, the bit line connected to the secondinterconnection, the semiconductor body connected to the bit line andextending in a first direction perpendicular to the substrate, theconductive layers arrayed in the first direction, the charge storageportion disposed between one of the conductive layers and thesemiconductor body.
 2. The device according to claim 1, wherein thefirst structure includes a third interconnection disposed in same layeras the first interconnection, and the second structure includes a viaelectrically connected to the third interconnection and penetratingthrough the second structure.
 3. The device according to claim 2,wherein the via includes a pad at an upper side.
 4. The device accordingto claim 1, wherein the first structure is attached to the secondstructure with an insulating film interposed.
 5. The device according toclaim 1, further comprising a bonding metal directly connected to thefirst interconnection and the second interconnection.
 6. The deviceaccording to claim 5, wherein the bonding metal is copper or copperalloy containing copper as a main component.
 7. The device according toclaim 4, further comprising a bonding metal directly connected to thefirst interconnection and the second interconnection, the insulatingfilm provided around the bonding metal.
 8. A semiconductor memory devicecomprising: a substrate; a control circuit disposed on the substrate; afirst interconnection disposed on the control circuit; a secondinterconnection disposed on the first interconnection and electricallyconnected to the first interconnection; a bit line connected to thesecond interconnection; a semiconductor body connected to the bit lineand extending in a first direction perpendicular to the substrate; aplurality of conductive layers arrayed in the first direction; and acharge storage portion disposed between one of the conductive layers andthe semiconductor body.
 9. The device according to claim 8, furthercomprising a third interconnection disposed in same layer as the firstinterconnection, and a via extending in the first direction andelectrically connected to the third interconnection.
 10. The deviceaccording to claim 9, wherein the via includes a pad at an upper side.11. The device according to claim 8, wherein the first interconnectionis attached to the second interconnection with an insulating filminterposed.
 12. The device according to claim 8, further comprising abonding metal directly connected to the first interconnection and thesecond interconnection.
 13. The device according to claim 12, whereinthe bonding metal is copper or copper alloy containing copper as a maincomponent.
 14. The device according to claim 11, further comprising abonding metal directly connected to the first interconnection and thesecond interconnection, the insulating film provided around the bondingmetal.